A constant liquid level low-pressure casting device and casting method without a riser tube

Abstract

The present invention discloses a low-pressure casting device with a constant liquid level and without a riser tube, comprising a double-chamber insulation furnace, the double-chamber insulation furnace comprising a riser chamber and a pressurizing chamber, a connecting channel being provided between the riser chamber and the pressurizing chamber, a control component for controlling the opening and closing of the connecting channel being provided on the connecting channel, a first heater and a second heater being provided at the bottom of the riser chamber and the pressurizing chamber respectively, a feeding port, a pressurizing pipe and a pressure relief pipe being provided on the pressurizing chamber, a bypass component for adjusting the pressure of the riser chamber being provided on the upper side of the riser chamber; the nitrogen supply and control system comprising a nitrogen generator, a control valve group and a control system for controlling the control valve. A casting method based on the above-mentioned device is also provided. The present invention solves the problem that during the filling process of molten metal, the molten metal fluctuates greatly with pressurization and pressure relief, oxide scale is generated between the molten metal and the furnace body, affecting the quality of the molten metal, and the filling speed is unstable, resulting in air entrainment in the product.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy low-pressure casting, and in particular to a constant liquid level low-pressure casting device without a riser tube and a casting method. Background Art

[0002] The existing low-pressure casting technology uses air pressure to move the molten metal in the insulation furnace into the mold cavity through a riser for casting. It has two prominent problems. The first problem is that the existing low-pressure casting must use a riser to input the aluminum alloy liquid into the mold cavity. The riser is immersed in high-temperature aluminum alloy liquid for a long time. The iron riser is easily corroded, causing the aluminum liquid to increase iron and even leak, resulting in waste. The second problem is that the riser height changes continuously with the increase in the number of casting molds, and the riser height of the aluminum alloy liquid also changes continuously. The speed at which the aluminum liquid enters the mold cavity fluctuates greatly, and the product quality consistency is poor.

[0003] In order to solve the problem of poor corrosion resistance of iron riser tubes, people invented ceramic riser tubes. Ceramic riser tubes are expensive, costing up to several thousand yuan each, and have poor resistance to sudden cooling and heating. During operations such as furnace changing or replenishing molten aluminum, they often break and become scrapped. In addition, slag nodules are easily generated on the inner wall of ceramic riser tubes, affecting the purity of the molten aluminum and the stability of the rising liquid.

[0004] In order to solve the problem of unstable casting quality caused by the drop in the liquid level in the furnace, people have adopted a pressure compensation method, that is, according to the drop in the liquid level caused by casting a mold, the corresponding air pressure is increased to compensate for the pressure increase required for the increase in the liquid height. Since the cross-section of the furnace is variable, the change of the liquid level with the number of castings is not a linear law. The compensation accuracy is not high, and it is difficult to stabilize the product quality.

[0005] The present invention is proposed to solve the problem of increased costs caused by the contamination or easy damage of the riser tube to the aluminum liquid in the existing low-pressure casting, and to solve the problem of unstable product quality caused by the continuous decrease of the liquid level in the existing low-pressure casting furnace with the increase of the number of castings. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects in the prior art and provide a constant liquid level low-pressure casting device without a riser tube to solve the problem that during the filling process of molten metal, the metal liquid fluctuates greatly with the pressurization and decompression, and oxide scale is generated between the metal liquid and the furnace body, which affects the quality of the metal liquid; the metal liquid level is controlled to be stable so that the filling stroke of each mold is consistent, avoiding the formation of a condensation layer, and because the stroke is guaranteed, the filling efficiency is improved; and the problem of unstable filling speed leading to air entrainment in the product is solved.

[0007] To achieve the above object, the present invention provides a riser-free constant liquid level low-pressure casting device, comprising:

[0008] A double-chamber holding furnace, the double-chamber holding furnace comprising a liquid riser chamber and a pressurizing chamber, a communication channel being provided between the liquid riser chamber and the pressurizing chamber, a control component being provided on the communication channel for controlling the opening and closing of the communication channel, a first heater and a second heater being provided at the bottom of the liquid riser chamber and the pressurizing chamber, respectively, a feeding port, a pressurizing pipe, and a pressure relief pipe being provided on the pressurizing chamber, a bypass component being provided on the upper side of the liquid riser chamber for adjusting the pressure of the liquid riser chamber, and a gate being provided at the top of the liquid riser chamber;

[0009] A nitrogen supply and control system includes a nitrogen generator, a control valve group, and a control system for controlling the control valve. The nitrogen generator is connected to the pressurized pipeline and the bypass component through the control valve.

[0010] Furthermore, the control assembly includes a stopper cylinder disposed on one side of the pressurized chamber and a pressurized chamber stopper connected to the stopper cylinder. A movable cavity for movement of the pressurized chamber stopper is defined in a side wall of the pressurized chamber, and the pressurized chamber stopper is positioned within the movable cavity. The movable cavity is configured to fully accommodate the pressurized chamber stopper, ensuring that the pressurized chamber stopper is not obstructed when the communicating channel is open, and that the pressurized chamber stopper can freely extend to seal the communicating channel when the communicating channel needs to be closed.

[0011] Furthermore, a sealed cavity is provided on the other side of the connecting channel relative to the active cavity. The sealed cavity is positioned to match the active cavity and sized to accommodate the pressurized chamber stopper rod. A plug-in portion is formed at the end of the pressurized chamber stopper rod, and an inclined stepped portion is formed between the plug-in portion and the pressurized chamber stopper rod. The shape of the sealed cavity matches the plug-in portion and the stepped portion. The provision of the sealed cavity allows the pressurized chamber stopper rod to be inserted, improving the sealing performance when closing the connecting channel. In particular, the coordination of the stepped portion and the plug-in portion further improves the sealing performance of the pressurized chamber stopper rod with respect to the connecting channel, preventing the flow of molten metal.

[0012] Furthermore, the pressurizing chamber is provided with a first pressure sensor, and the upper end of the liquid lifting chamber is provided with a liquid level sensor. The first pressure sensor and the liquid level sensor can monitor the pressure in the pressurizing chamber and the height of the liquid level in the liquid lifting chamber, coordinating with the control system and other components.

[0013] Furthermore, the bypass assembly includes a bypass pipe connected to the upper side of the lift chamber, a bypass cylinder disposed on one side of the bypass pipe, and a gas brick connected to the bypass cylinder. The gas brick is placed between the bypass pipe and the lift chamber to separate them. A bypass valve is disposed within the bypass pipe to open and close the bypass pipe. The bypass pipe is connected to the nitrogen generator. Nitrogen enters the lift chamber through the gas brick, but molten metal cannot flow out of the gas brick, thus achieving a one-way flow.

[0014] Furthermore, the control valve assembly includes a proportional valve assembly and an angle seat valve. The pressurized pipeline is provided with a first pipeline and a second pipeline connected in parallel, and the angle seat valve and proportional valve assembly are respectively provided on the first pipeline and the second pipeline. The angle seat valve and proportional valve form a multi-threaded nitrogen delivery mode, which can more accurately control the nitrogen flow rate and thus the filling speed of the molten metal.

[0015] Furthermore, the proportional valve group includes a control proportional valve and a detection proportional valve, and the pressurized pipeline is further provided with a third pipeline connected in parallel with the first pipeline and the second pipeline. The control proportional valve is provided on the second pipeline, and the detection proportional valve is provided on the third pipeline. A first safety valve and a second safety valve are provided on the second pipeline and the third pipeline, respectively. A pressure transmitter is provided behind the detection proportional valve (73). By controlling the nitrogen flow rate through the dual proportional valves in conjunction with the first pressure sensor, the metal liquid filling speed can be more accurately controlled, so that the filling speed changes linearly, thereby solving the problem of metal liquid generating air entrainment caused by the unstable filling speed of the aluminum liquid.

[0016] A constant liquid level low-pressure casting method without a riser tube is also provided, comprising the following steps:

[0017] S1. Keeping the molten metal warm: Open the pressurizing chamber stopper between the lifting chamber and the pressurizing chamber to make the liquid levels in the lifting chamber and the pressurizing chamber equal; start the first heater and the second heater in the lifting chamber and the pressurizing chamber to control the temperature of the molten metal in the double-chamber holding furnace to the set temperature and keep it warm;

[0018] S2. Pressurized filling: Open the angle seat valve and proportional valve group of the nitrogen inlet pipe to increase the pressure in the pressurized chamber. When the pressure sensor in the pressurized chamber detects that the pressure in the furnace has reached a first pressure value and the nitrogen has filled the entire pressurized chamber, the angle seat valve is closed and the proportional valve group remains open, increasing the pressure in the pressurized chamber. The molten metal in the rising chamber begins to rise slowly. The control system continuously monitors the pressure in the pressurized chamber and continuously adjusts the opening and closing state of the proportional valve group to ensure that the molten metal rises steadily at a first speed. When the liquid level reaches the gate position, the proportional valve group opens wider, increasing the rising speed of the molten metal to a second speed. The molten metal quickly fills the mold cavity, and the second speed is greater than the first speed.

[0019] S3, pressure-maintaining solidification: The pressure in the pressurizing chamber continues to increase, and the molten metal in the lifting chamber begins to slowly rise to compensate for the liquid contraction of the molten metal. The control system continuously monitors the pressure in the pressurizing chamber and continuously adjusts the opening and closing state of the proportional valve group. The pressure in the lifting chamber is maintained at the set second pressure value, waiting for the molten metal to solidify.

[0020] S4, pressure relief and reflux: When the pressure holding time reaches the set value, the bypass valve cylinder opens the bypass valve and introduces nitrogen into the bypass valve to reduce the pressure in the lifting chamber. At the same time, the pressure relief valve starts to relieve pressure. When it is detected that the liquid level in the lifting chamber drops to the set position below the gate, the pressure relief is stopped. The pressurization chamber stopper closes the communication channel between the pressurization chamber and the lifting chamber, so that the liquid level in the lifting chamber no longer drops and remains at a constant position, completing the casting;

[0021] S5. Replenishing molten metal: Open the feeding port and the stopper rod of the pressurizing chamber, add the qualified molten metal into the double-chamber holding furnace, and when the liquid level in the rising chamber reaches the set position, close the stopper rod between the rising chamber and the pressurizing chamber, and repeat the steps from S1 to S3.

[0022] Furthermore, in step S2, the first set value is 0-18 KPa, the first speed is 20-50 mm / s, and the second speed is 50-100 mm / s.

[0023] Furthermore, the setting position in step S4 is 30-50 mm below the gate.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention eliminates the need for a riser pipe, thereby reducing production costs, increasing mold filling speed, and preventing accidents such as riser pipe rupture and blockage, thereby improving casting stability.

[0026] (2) During casting, the liquid level and the lifting height of the double chambers can be kept constant, eliminating the difference in the quality of castings of different molds. The molten metal between the lifting chamber and the pressurizing chamber will not flow back, ensuring that the lifting and filling stroke is consistent each time, and the molten metal is always suspended in a fixed position below the gate of the lifting chamber, shortening the molten metal filling stroke, while reducing the reflux of the molten metal, avoiding the formation of a condensation layer on the furnace wall, and improving product quality.

[0027] (3) The pressure in the pressurized chamber is controlled by a closed loop. The pressure controlled by the proportional valve group is compared with the pressure in the pressurized chamber. The pressure is corrected in real time, which maintains a stable output of pressure and makes the produced products uniform.

[0028] (4) By controlling the nitrogen flow rate through the dual proportional valve, the metal liquid filling speed can be controlled more accurately, making the filling speed change linearly, thus solving the problem of air entrainment in the metal liquid caused by the unstable filling speed of the aluminum liquid.

[0029] (5) The temperature of the molten metal is controlled by zones, which compensates in real time for the temperature drop of the molten metal caused by feeding, pouring, pressurization, etc., so that the pouring temperature of the molten metal is consistent. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 This is a structural schematic diagram of a constant liquid level low-pressure casting device without a riser tube provided by the present invention;

[0032] Figure 2 This is a schematic diagram of a connected and pressurized state of a constant liquid level low-pressure casting device without a riser tube provided by the present invention;

[0033] Figure 3 This is a schematic diagram of a state in which the liquid level of a constant liquid level low-pressure casting device without a riser provided by the present invention falls back;

[0034] Figure 4 It is a gas path principle diagram of the present invention.

[0035] Included in the diagram are:

[0036] 1. Double-chamber holding furnace; 11. Pressurizing chamber; 111. Active chamber; 112. Sealed chamber; 113. Second heater; 114. First pressure sensor; 115. Feeding port; 116. Pressurizing pipe; 1161. First pipe; 1162. Second pipe; 1163. Third pipe; 1164. First safety valve; 1165. Second safety valve; 117. Pressure relief pipe; 1171. Pressure relief valve; 1172. Third safety valve; 12. Lifting chamber; 121. First heater; 122. Liquid level sensor; 123. Gate; 124, docking flange; 13, connecting channel; 14, control assembly; 141, stopper cylinder; 142, pressurized chamber stopper; 1421, plug-in part; 1422, stepped part; 2, molten metal; 3, bypass assembly; 31, bypass pipe; 32, bypass cylinder; 33, breathable brick; 34, bypass valve; 4, mold; 5, nitrogen generator; 6, gas storage tank; 7, control valve group; 71, angle seat valve; 72, control proportional valve; 73, detection proportional valve; 731, pressure transmitter; 8, oil-water separator; 9, dryer. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solution in this embodiment of the present invention in conjunction with the drawings in this embodiment of the present invention. Obviously, the embodiment described is only one embodiment of the present invention, not all embodiments of the present invention. Based on this embodiment of the present invention, all other embodiments of the present invention obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0038] Please refer to Figures 1 to 4 The first embodiment of the present invention provides a low-pressure casting device with a constant liquid level and no riser tube, comprising:

[0039] The double-chamber holding furnace 1 includes a liquid rising chamber 12 and a pressurizing chamber 11, wherein the volume of the pressurizing chamber 11 is larger than that of the liquid rising chamber 12, ensuring that the liquid rising chamber 12 can be filled during operation to avoid insufficient molten metal 2. A connecting passage 13 is provided between the liquid rising chamber 12 and the pressurizing chamber 11, and a control component 14 for controlling the opening and closing of the connecting passage 13 is provided on the connecting passage 13. In this embodiment, the control component 14 includes a stopper rod cylinder 141 provided on one side of the pressurizing chamber 11 and a pressurizing chamber stopper rod 142 connected to the stopper rod cylinder 141. A stopper rod 142 for the pressurizing chamber is provided on the side wall of the pressurizing chamber 11. The rod 142 moves in the active cavity 111, and the pressurized chamber stopper rod 142 is placed in the active cavity 111. In order to increase the blocking effect of the pressurized chamber stopper rod 142 on the connecting channel 13, a closed cavity 112 is provided on the other side of the connecting channel 13 relative to the active cavity 111. The closed cavity 112 is adapted to the position of the active cavity 111. The size of the closed cavity 112 matches the pressurized chamber stopper rod 142. A plug-in portion 1421 is formed at the end of the pressurized chamber stopper rod 142. An inclined step portion 1422 is formed between the plug-in portion 1421 and the pressurized chamber stopper rod 142. The shape of the closed cavity 112 matches the plug-in portion 1421 and the step portion 1422.

[0040] like Figure 1 As shown, a first heater 121 and a second heater 113 are respectively provided at the bottom of the lifting chamber 12 and the pressurizing chamber 11, and a first pressure sensor 114 is also provided at the pressurizing chamber 11. A liquid level sensor 122 is provided at the upper end of the lifting chamber 12. The first heater 121 and the second heater 113 are used to heat the molten metal 2 in the lifting chamber 12 and the pressurizing chamber 11 to maintain the temperature consistency of the molten metal 2 in the two chambers. The first pressure sensor 114 is used to cooperate with the control system to monitor the pressure in the pressurizing chamber 11 in real time, so as to facilitate the control system to control the flow rate of nitrogen release and thus control the internal pressure of the pressurizing chamber 11. Similarly, the liquid level sensor 122 monitors the liquid level position of the lifting chamber 12.

[0041] A feeding port 115, a pressurizing pipe 116 and a pressure relief pipe 117 are provided on the pressurizing chamber 11. A bypass assembly 3 for adjusting the pressure of the lifting chamber 12 is provided on the upper side of the lifting chamber 12. The bypass assembly 3 includes a bypass pipe 31 connected to the upper side of the lifting chamber 12, a bypass cylinder 32 provided on one side of the bypass pipe 31, and an air brick 33 connected to the bypass cylinder 32. The air brick 33 is placed between the bypass pipe 31 and the lifting chamber 12 to separate the two. A bypass valve 34 for opening and closing the bypass pipe 31 is provided in the bypass pipe 31. A gate 123 is provided at the top of the lifting chamber 12. A docking flange 124 for mounting the mold 4 is provided on the side of the gate 123. The mold 4 is mounted through the docking flange 124.

[0042] The other end of the pressure relief pipe 117 is led out to the outside of the double-chamber insulation furnace 1, and can be connected to external recovery equipment to recover waste gas. A pressure relief valve 1171 is provided at the output end of the pressure relief pipe 117 to control the opening and closing of the pressure relief pipe 117. At the same time, in order to increase safety, a third safety valve 1172 is also provided on the pressure relief pipe 117. The third safety valve 1172 is a one-way valve.

[0043] The nitrogen supply and control system includes a nitrogen generator 5, a control valve group 7, and a control system for controlling the control valve. The control system adopts a PLC controller. The nitrogen generator 5 is connected to the pressurized pipe 116 and the bypass assembly 3 through the control valve. To facilitate the storage of nitrogen, in this embodiment, there is still a gas storage tank 6 between the nitrogen generator 5 and the control valve group 7. The gas storage tank 6 is connected to the bypass pipe 31 and the pressurized pipe 116 respectively; Figure 4 As shown, the control valve group 7 of this embodiment includes a proportional valve group and an angle seat valve 71. A first pipe 1161, a second pipe 1162 and a third pipe 1163 are provided in parallel on the pressurized pipe 116, wherein the proportional valve group includes a control proportional valve 72 and a detection proportional valve 73, and a pressure transmitter 731 is provided behind the detection proportional valve 73. The angle seat valve 71, the control proportional valve 72 and the detection proportional valve 73 are respectively provided on the first pipe 1161, the second pipe 1162 and the third pipe 1163. To further ensure safety, a first safety valve 1164 and a second safety valve 1165 are respectively provided on the second pipe 1162 and the third pipe 1163. The first safety valve 1164 and the second safety valve 1165 are both one-way valves.

[0044] As a preferred method, when the nitrogen generator 5 generates nitrogen, a certain amount of pollutants such as water vapor will be generated. If such pollutants are directly input into the pressurized chamber 11, the purity of the molten metal 2 will be affected to a certain extent, resulting in the appearance of defective products. In order to avoid interference with the composition of the molten metal 2, an oil-water separator 8 and a dryer 9 are sequentially arranged between the gas storage tank 6 and the control valve to purify the nitrogen entering the control valve. In order to ensure the pressurization requirement of the pressurized chamber 11, the pressure of the nitrogen in the gas storage tank 6 is set to 0.6-0.8Mpa, corresponding to the control of the pressure in the tank. The gas storage tank 6 of the present invention can adopt a pressure gas storage tank 6, which can be used by directly adjusting the pressure of the nitrogen in the tank through the pressure gas storage tank 6.

[0045] A constant liquid level low-pressure casting method without a riser tube is also provided, comprising the following steps:

[0046] S1. Keeping the molten metal 2 warm: open the pressurized chamber stopper rod 142 between the lifting chamber 12 and the pressurizing chamber 11. Specifically, the pressurizing chamber stopper rod 142 is driven to move by the stopper rod cylinder 141, so that the pressurizing chamber stopper rod 142 is retracted into the movable cavity 111. At this time, the pressurizing chamber 11 is connected with the lifting chamber 12, and the molten metal 2 in the pressurizing chamber 11 will enter the lifting chamber 12 through the connecting channel 13, so that the liquid levels of the lifting chamber 12 and the pressurizing chamber 11 are at the same height; start the first heater 121 and the second heater 113 of the lifting chamber 12 and the pressurizing chamber 11, so that the temperature of the molten metal 2 in the double-chamber insulation furnace 1 is controlled at the set temperature of 690℃-780℃ and kept warm.

[0047] S2. Pressurized filling: Open the angle seat valve 71 and the proportional valve group of the nitrogen inlet pipe, and the nitrogen quickly fills the entire pressurized chamber 11 to increase the pressure in the pressurized chamber 11. When the pressure sensor in the pressurized chamber 11 detects that the pressure in the furnace reaches the first pressure value of 0-18Kpa, after the nitrogen fills the entire pressurized chamber 11 (that is, when the liquid level sensor 122 detects that the liquid level in the lifting chamber 12 begins to rise), the angle seat valve 71 is closed, and the proportional valve group is still in the open state, continuing to increase the pressure in the pressurized chamber 11. The metal liquid 2 in the lifting chamber 12 begins to rise slowly. The control system continuously monitors the pressure in the pressurized chamber 11 and continuously adjusts the opening and closing state of the proportional valve group to make the metal liquid 2 rise steadily at a first speed of 20-50mm / s. Specifically, when the pressure value of the pressurized chamber 11 reaches the first pressure value, the angle seat valve 71 is closed, and the proportional valve 72 and the detection proportional valve are controlled. For example, the opening of the valve 73 is reduced, and a small flow of nitrogen is introduced to increase the pressure in the pressurizing chamber 11. According to Pascal's principle, the liquid level in the lifting chamber 12 rises at a set first speed under the action of pressure. At the same time, the first pressure sensor 114 detects the pressure change in the pressurizing chamber 11 in real time. The pressure transmitter 731 also detects the proportional valve 73 to detect the real-time pressure of the proportional valve 73, and converts the air pressure signal into an electrical signal, which is fed back to the PLC controller. The PLC controller compares the pressure of the pressure transmitter 731 with the pressure in the pressurizing chamber 11, thereby adjusting the opening of the proportional valve 73 to keep the pressure in the pressurizing chamber 11 at the set pressure level. When the pressure detected by the first pressure sensor 114 is lower than the set pressure, the control system adjusts the opening of the proportional valve 73 to increase the flow of nitrogen to maintain the pressure in the pressurizing chamber 11 stable.

[0048] When the liquid level reaches the gate 123, the proportional valve group opens wider, increasing the rising speed of the molten metal 2 to a second speed of 50-100 mm / s. The molten metal 2 quickly fills the mold cavity, wherein the second speed is greater than the first speed.

[0049] S3, pressure-maintaining solidification: The pressure in the pressurizing chamber 11 is continuously increased, and the molten metal 2 in the lifting chamber 12 begins to slowly rise to compensate for the liquid contraction of the molten metal 2. The control system continuously monitors the pressure in the pressurizing chamber 11 and continuously adjusts the opening and closing state of the proportional valve group. The pressure in the lifting chamber 12 is maintained at a set second pressure value, and the pressure is maintained until the molten metal 2 solidifies. The second pressure value is 30-120 kPa.

[0050] S4, pressure relief and reflux: When the pressure holding time reaches the set value, the bypass valve 34 cylinder opens the bypass valve 34 and introduces nitrogen into the bypass valve 34 to reduce the pressure in the lifting chamber 12. At the same time, the pressure relief valve 1171 starts to relieve pressure. When it is detected that the liquid level in the lifting chamber 12 has dropped to the set position, specifically 30-50 mm below the gate 123, the pressure relief is suspended. The pressurizing chamber stopper rod 142 closes the communication channel 13 between the pressurizing chamber 11 and the lifting chamber 12, so that the liquid level in the lifting chamber 12 no longer drops and remains at a constant position, completing the casting;

[0051] S5. Replenishing the molten metal 2: Open the feeding port 115 of the pressurizing chamber 11 and the pressurizing chamber stopper rod 142, and add the qualified molten metal 2 into the double-chamber holding furnace 1. When the liquid level of the rising chamber 12 reaches the set position, close the pressurizing chamber stopper rod 142 between the rising chamber 12 and the pressurizing chamber 11, and repeat the steps S1 to S3.

[0052] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A constant liquid level low-pressure casting device without a riser, characterized in that: include: A double-chamber insulation furnace (1), comprising a liquid raising chamber (12) and a pressurizing chamber (11), a communication channel (13) being provided between the liquid raising chamber (12) and the pressurizing chamber (11), a control component (14) for controlling the opening and closing of the communication channel (13) being provided on the communication channel (13), a first heater (121) and a second heater (113) being provided at the bottoms of the liquid raising chamber (12) and the pressurizing chamber (11), respectively, a feeding port (115), a pressurizing pipe (116) and a pressure relief pipe (117) being provided on the pressurizing chamber (11), a bypass component (3) for adjusting the pressure of the liquid raising chamber (12) being provided on the upper side of the liquid raising chamber (12), and a gate (123) being provided at the top of the liquid raising chamber (12); A nitrogen supply and control system, comprising a nitrogen generator (5), a control valve group (7), and a control system for controlling the control valve, wherein the nitrogen generator (5) is connected to the pressurized pipeline (116) and the bypass assembly (3) via the control valve; The control valve group (7) includes a proportional valve group and an angle seat valve (71), a first pipeline (1161) and a second pipeline (1162) are provided on the pressurized pipeline (116), the angle seat valve (71) and the proportional valve group are respectively provided on the first pipeline (1161) and the second pipeline (1162), the proportional valve group includes a control proportional valve (72) and a detection proportional valve (73), and the pressurized pipeline (116) is also provided with a first pipeline (1161) and a second pipeline (1162). 1161) and a third pipeline (1163) connected in parallel with the second pipeline (1162), the control proportional valve (72) is arranged on the second pipeline (1162), the detection proportional valve (73) is arranged on the third pipeline (1163), a first safety valve (1164) and a second safety valve (1165) are respectively arranged on the second pipeline (1162) and the third pipeline (1163), and a pressure transmitter (731) is arranged behind the detection proportional valve (73).

2. A constant liquid level low pressure casting device without a riser tube according to claim 1, characterized in that: The control assembly (14) comprises a stopper rod cylinder (141) arranged on one side of the pressurized chamber (11) and a pressurized chamber stopper rod (142) connected to the stopper rod cylinder (141). An active cavity (111) for the pressurized chamber stopper rod (142) to move is provided on the side wall of the pressurized chamber (11), and the pressurized chamber stopper rod (142) is placed in the active cavity (111).

3. A constant liquid level low pressure casting device without a riser tube according to claim 2, characterized in that: A sealed chamber (112) is provided on the other side of the connecting channel (13) relative to the active chamber (111). The position of the sealed chamber (112) is adapted to that of the active chamber (111). The size of the sealed chamber (112) matches that of the pressurized chamber stopper rod (142). The end of the pressurized chamber stopper rod (142) forms a plug-in portion (1421). An inclined stepped portion (1422) is formed between the plug-in portion (1421) and the pressurized chamber stopper rod (142). The shape of the sealed chamber (112) matches that of the plug-in portion (1421) and the stepped portion (1422).

4. The constant liquid level low pressure casting device without a riser tube according to claim 1, characterized in that: The pressurizing chamber (11) is further provided with a first pressure sensor (114), and the upper end of the liquid raising chamber (12) is provided with a liquid level sensor (122).

5. The constant liquid level low pressure casting device without a riser tube according to claim 1, characterized in that: The bypass assembly (3) comprises a bypass pipe (31) communicating with the upper side of the liquid lifting chamber (12), a bypass cylinder (32) arranged on one side of the bypass pipe (31), and a gas-permeable brick (33) connected to the bypass cylinder (32). The gas-permeable brick (33) is placed between the bypass pipe (31) and the liquid lifting chamber (12) to separate the two. A bypass valve (34) for opening and closing the bypass pipe (31) is arranged in the bypass pipe (31). The bypass pipe (31) is connected to the nitrogen generator (5).

6. The casting method of a constant liquid level low-pressure casting device without a riser tube according to any one of claims 1 to 5, characterized in that: The steps include: S1, keeping the molten metal (2) warm: opening the pressurizing chamber stopper rod (142) between the lifting chamber (12) and the pressurizing chamber (11) to make the liquid levels in the lifting chamber (12) and the pressurizing chamber (11) equal; starting the first heater (121) and the second heater (113) in the lifting chamber (12) and the pressurizing chamber (11) to control the temperature of the molten metal (2) in the double-chamber heat-insulating furnace (1) to a set temperature and keep the temperature warm; S2, pressurized filling: open the angle seat valve (71) and the proportional valve group of the nitrogen inlet pipe to increase the pressure in the pressurized chamber (11). When the pressure sensor in the pressurized chamber (11) detects that the pressure in the furnace reaches a first pressure value and the nitrogen fills the entire pressurized chamber (11), the angle seat valve (71) is closed and the proportional valve group is still in an open state, increasing the pressure in the pressurized chamber (11). The metal liquid (2) in the liquid raising chamber (12) begins to rise slowly. The control system continuously monitors the pressure in the pressurized chamber (11) and continuously adjusts the opening and closing state of the proportional valve group to make the metal liquid (2) rise steadily at a first speed. When the liquid level reaches the gate (123), the opening of the proportional valve group is increased to increase the rising speed of the metal liquid (2) to a second speed. The metal liquid (2) quickly fills the mold cavity, wherein the second speed is greater than the first speed. S3, pressure-maintaining solidification: the pressure in the pressurizing chamber (11) is continuously increased, and the molten metal (2) in the lifting chamber (12) begins to slowly rise to supplement the liquid contraction of the molten metal (2). The control system continuously monitors the pressure in the pressurizing chamber (11) and continuously adjusts the opening and closing state of the proportional valve group. The pressure in the lifting chamber (12) is maintained at the set second pressure value, and the molten metal (2) is waited for solidification. S4, pressure relief and reflux: When the pressure holding time reaches the set value, the bypass valve (34) cylinder opens the bypass valve (34) and introduces nitrogen into the bypass valve (34) to reduce the pressure in the liquid lifting chamber (12). At the same time, the pressure relief valve (1171) starts to relieve pressure. When it is detected that the liquid level in the liquid lifting chamber (12) drops to the set position below the gate (123), the pressure relief is suspended. The pressurizing chamber stopper rod (142) closes the communication channel (13) between the pressurizing chamber (11) and the liquid lifting chamber (12), so that the liquid level in the liquid lifting chamber (12) no longer drops and remains at a constant position, completing the casting. S5. Supplementing the molten metal (2): Open the feeding port (115) of the pressurizing chamber (11) and the pressurizing chamber stopper rod (142), and add the qualified molten metal (2) into the double-chamber insulation furnace (1). When the liquid level of the rising chamber (12) reaches the set position, close the pressurizing chamber stopper rod (142) between the rising chamber (12) and the pressurizing chamber (11), and repeat the steps S1 to S3 in a cycle.

7. A riser-free constant liquid level low-pressure casting method according to claim 6, characterized in that: In step S2, the first set value is 0-18 KPa, the first speed is 20-50 mm / s, and the second speed is 50-100 mm / s.

8. The method for constant liquid level low pressure casting without a riser tube according to claim 6, characterized in that: The setting position in step S4 is 30-50 mm below the gate (123).

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